Wednesday, March 12, 2014

Gustav Kirchhoff and the Fundamentals of Electrical Circuits

Kirchhoff (left), Bunsen (middle)
Roscoe (right)
On March 12, 1824, German physicist Gustav Robert Kirchhoff was born. He is best known for his contribution to the fundamental understanding of electrical circuits, spectroscopy, and the emission of black-body radiation by heated objects.

Gustav Robert Kirchhoff was born to a lawyer in Königsberg, East Prussia, where he also enrolled ath the Albertus University. He took classes of Franz Neumann and Friedrich Julius Richelot and it is said, that Kirchoff's rare mathematical talent adapted him to the use of analytical aids to such an extent that he could always readily bring the best methods to the solution of any problem. In 1847, Kirchhoff graduated and married Richelot's daughter Clara. In the same year, the couple moved to Berlin, where Kichhoff worked at a private teacher and stayed there until he received a professorship at the University of Breslau.

In 1845, when he was still a student, Kirchhoff began formulating his circuit laws, which are now ubiquitous in electrical engineering. This work was achieved during a seminar exercise and was followed by other valuable papers on electrical questions, among which were those on conduction in curved sheets, on Ohm's law, on the distribution of electricity on two influencing spheres, on the discharge of the Leyden jar, on the motion of electricity in submarine cables, etc. Among them also is a paper on the determination of the constant on which depends the intensity of induced currents, in which is involved the absolute measurement of electric resistance in a definite wire.

He continued his career at Breslau and later Heidelberg, where he had been chosen regular professor in physics. There he lived and taught for two decades, attracting many experts with his work. Robert von Helmholtz is supposed to have said that there was only little known about Kirchhoff in the general public, but "his refined, animated speech, his courteous and attractive demeanor, his fine sense of humor and his wit, soon won him the liking of all men with whom he came in contact".

The discovery of the spectrum analysis ranks among the greatest achievements in the history of science. Isaac Newton once succeeded in separating white sunlight into its colored constituents. Wollaston discovered in 1802 the dark lines in the spectrum and Joseph Fraunhofer investigated those lines, fixed the position of more than five hundred of them, and marked the principal groups with letters. Kirchhoff then managed to find the key for these phenomena. He discovered the law of the relation of emission and absorption and thereby furnished the theoretical basis of spectrum analysis. Kirchhoff's first publication on this subject appeared in the monthly reports of the Berlin Academy in 1859, followed by a rapid succession of papers describing the researches of Kirchhoff and Bunsen upon the solar spectrum and the spectra of the elements. A few years later, he was awarded the Rumford Medal for his research.

Gustav Kirchhoff passed away on 17 October, 1887. 

At yovisto, you may be interested ina video lecture on Designing Electrical Circuits at UC Berkeley.



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